Referring back to orig. post -
As mentioned it's best to just install gnome-session-flashback (not fallback, not gnome-panel

You seemed to indicate that after 'your tweaking' that upon reboot the session wouldn't load, if so then look at what you did..

Reason for it not to load -
missing a required_component, most obvious would be gnome-screensaver, listed in /usr/share/gnome-session/sessions/whatever.session

Other possibilities -
I've seen on rare occasion where the session will actually load but take an inordinate amount of time to do so, 30 - 60 sec's
Or again quite rarely it just won't load, hasn't happened in some time now
In both cases, at least here, removing any file(s) in ~/.dbus/session-bus proved helpful